In a traditional networking mode, the service is interrupted once a link is cut. The interruption of certain important services such as telecom service and bank service brings huge negative impact and economic loss. To avoid such consequences, redundant devices are networked to ensure that the standby device takes over services automatically in the case of failure of the active device, which ensures continuity of the services and is known as two-node cluster hot backup.
When enterprises or persons distributed in different areas communicate through the Internet, the communication needs to traverse unknown networks because the communication parties are located in different geographic regions, which leads to uncertainty of data security on the Internet. The IP Security (IPSec) protocol enables enterprises and users in different geographical regions to set up and manage Virtual Private Network (VPNs), and authenticates and encrypts transmitted data packets to prevent the data from being illegally viewed or altered when the data is transmitted in the Intranet or the Internet.
In the conventional two-node hot backup mode, the active device sends information as packets to be backed-up to the standby device at intervals. When the active device fails, certain information generated after the last backup (such as serial number of the data) is lost. Consequently, after switchover to the standby device, the data packets sent by the former standby device are mistakenly regarded as old packets and are discarded, which leads to interruption of certain services such as IPSec VPN services.